binman: Add support for building a binmanu PyPi package

Create the necessary files to build this new package.

It is not actually clear whether this is useful, since buildman has no
purpose outside U-Boot.

Move the main program into a function so that it can easily be called by
the PyPi-created script.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index bf6abe5..c00683b 100644
--- a/Makefile
+++ b/Makefile
@@ -2285,6 +2285,7 @@
 	scripts/make_pip.sh patman ${PIP_ARGS}
 	scripts/make_pip.sh buildman ${PIP_ARGS}
 	scripts/make_pip.sh dtoc ${PIP_ARGS}
+	scripts/make_pip.sh binman ${PIP_ARGS}
 
 help:
 	@echo  'Cleaning targets:'